(1) Field of the Invention
The present invention pertains to a bearing supporting a rotating shaft of an electrical device, for example an electric motor, and a sleeve that is mounted on the shaft in engagement with the bearing. Together the bearing and sleeve function to simplify the construction of the electrical device by eliminating one of a pair of retaining rings from the shaft that was previously necessary to hold the shaft and bearing in relative positions, and by eliminating a second retaining ring from the shaft that was used as a locator to positively locate a machined surface on the housing of the electrical device relative to the second ring and to positively locate a rotating component on the end of the shaft.
(2) Description of Related Art
In home appliances that employ water pumps driven by electric motors, for example dishwashers or clothes washers, the housing of the water pump is often mounted against the housing or end shield of the motor to reduce the amount of the interior area of the appliance that is occupied by the water pump and motor. In addition, mounting the pump housing against a portion of the motor housing positively locates the pump relative to the motor and positively locates the motor shaft in the pump housing interior. Proper positioning of the pump housing relative to the motor and the motor shaft is necessary to insure that the pump impeller mounted on the motor shaft inside the pump housing is properly positioned relative to the pump housing interior surfaces to prevent the pump impeller from contacting with the pump housing interior surfaces on operation of the pump and possibly seizing up the pump.
In order to insure that a pump housing and a pump impeller contained in the pump housing are both properly positioned relative to each other when the pump housing and pump impeller are assembled to the motor, the motor shaft is often used as a reference point in positioning a machined surface on the electric motor housing against which the pump housing seats. The motor shaft is also used as a reference point for the impeller of the pump, to properly position the impeller in the interior of the pump housing. Thus, the motor shaft is used as a reference point to properly position both the pump housing relative to the motor housing and to properly position the impeller relative to the pump housing interior for proper operation of the water pump.
One example of a prior art electric motor 12 is shown in FIG. 1. The particular construction of the electric motor 12 is typical of most electric motors and therefore the construction is shown schematically and only one end of the electric motor, the end from which the motor shaft 14 extends, is shown in FIG. 1. The motor is shown positioned with the motor shaft 14 oriented vertically. The motor could also be positioned with the shaft 14 oriented horizontally. The motor in FIG. 1 is an open-frame construction type of motor having a pair of end shields 18, only one of which is shown in FIG. 1, secured to opposite axial ends of the motor. The end shield 18 shown in FIG. 1 has a shaft opening 22 at its center. The two end shields are secured to axially opposite ends of the motor stator core 24 covering over the stator winding end turns 26. The rotor 28 of the motor is mounted on the motor shaft 14 and is positioned in the interior bore of the stator core 24. The shaft 14 is supported at its axially opposite ends by a pair of bearings mounted in the end shields. FIG. 1 shows only one of the bearings 32 mounted in the shaft opening 22 of the motor end shield.
The motor 12 is shown in FIG. 1 positioned with its shaft 14 oriented vertically where the shaft rotates a rotary component of a home appliance, for example an impeller of a pump in a dishwasher or clothes washer. In order to use the motor shaft 14 as a point of reference for locating machined surfaces on the housing of the motor 12 and for locating the pump housing and pump impeller relative to the shaft, it is necessary that the shaft 14 not move axially (i.e. in a direction along the shaft center axis 34) relative to the motor. In the prior art solution to prevent axial movement of the shaft 14, a pair of annular grooves 36, 38 are machined in the shaft. The grooves 36, 38 are positioned on the shaft an axial distance from each other that corresponds to the axial width of the bearing 32. With the shaft grooves 36, 38 positioned on opposite sides of the bearing 32, retainer rings, for example C-type retainer rings or E-type retainer rings 42, 44 are pressed into the two shaft grooves 36, 38 on opposite sides of the bearing 32 to secure the shaft in its axial position relative to the bearing. This in turn secures the shaft 14 in its axial position relative to the motor 12. This enables use of the shaft 14 as a reference point for locating a machined seating surface on the housing of the motor 12 when the motor is used with a pump, and for locating a rotating component of the pump, for example the impeller, relative to the shaft and the pump housing.
To locate the pump housing and pump impeller relative to the shaft 14, a third annular groove 46 is formed in the shaft and an additional retainer ring 48 is inserted into the groove. The additional retainer ring 48 is used as a point of reference to positively locate the pump impeller 52 relative to the shaft, relative to the end shield 18 of the motor 12, and relative to the pump housing. With the impeller 52 positively located relative to the shaft 14 and the motor 12, and the proper position of the impeller relative to the pump housing being known, the additional retainer ring 48 is used as a point of reference for positively locating a machined surface 54 on the end shield 18 of the motor 12 to serve as a seating surface with the pump housing 56 (represented by dashed lines in FIG. 1). Thus, the additional retainer ring 48 serves the dual purpose of positively locating the pump impeller 52 on the shaft 14 and positively locating the machined surface 54 on the motor end shield 18 that is then used to properly locate the pump housing 56 relative to the motor shaft 14.
However, problems were encountered in the above-described apparatus and method of locating the pump impeller 52 and locating the machined surface 54 relative to the motor end shield 18. In assembling the impeller 52 on the end of the motor shaft 14, the impeller would often be rotated on the shaft as it was pressed downward over the top end of the shaft as shown in FIG. 1. Rotating the impeller 52 as it was pressed downwardly onto the shaft 14 would at times cause the third retainer ring 48 to become dislodged from its shaft groove 46. This would result in the impeller 52 being improperly positioned on the shaft 14. The improperly positioned impeller would contact the interior of the pump housing when rotated by the motor which would detract from the proper operation of the pump. In addition, in using the third retainer ring 48 as a locator for machining the seating surface on the motor end shield, the motor would typically be mounted on a mandril with an indexing part of the mandril engaging against the third retainer ring. The engagement of the mandril indexing part with the third retainer ring would positively locate the plane of the machined seating surface to be formed on the motor end shield. The machined surface would be cut or ground into the cast metal of the end shield relative to the position of the third retainer ring 48 on the motor shaft. The third retainer ring 48 becoming dislodged from its shaft groove 46 would result in the seating surface machined on the motor housing being improperly positioned. As a result, the pump housing would be assembled in a misaligned position on the motor end shield 18, presenting the potential for the impeller 52 contacting with the pump housing interior and seizing up.
The present invention overcomes the disadvantages associated with using a retainer ring as a locating device for positively locating a rotating component on a rotary shaft and for positively locating a machined surface relative to the rotary shaft. The present invention provides a tubular sleeve spacer that is positioned on the shaft of the rotary device between one of the bearings supporting the shaft and the rotating component mounted on the shaft.
In the description of the invention to follow, the terms xe2x80x9crotary devicexe2x80x9d and xe2x80x9crotating componentxe2x80x9d are used to broadly describe the environment in which the invention may be used. In the preferred embodiment, the xe2x80x9crotary devicexe2x80x9d is an electric motor used in a home appliance. The electric motor drives a water pump of the home appliance. Thus, in the preferred embodiment of the invention the xe2x80x9crotating componentxe2x80x9d is an impeller of the appliance pump. It should be understood that the concept of the invention may be employed in operative environments other than that disclosed in describing the preferred embodiment of the invention. For example, the xe2x80x9crotary devicexe2x80x9d could be some other type of motor or other type of electrical device, for example a generator. In addition, the xe2x80x9crotating componentxe2x80x9d could be some other type of component rotated with the shaft, for example a fan or pulley. Therefore, although the invention is described as being employed in the environment of an electric motor and a pump impeller driven by the motor, it should be understood that there are other equivalent operative environments in which the invention is equally well suited for use.
In use of the sleeve spacer of the invention, two of the annular grooves in the shaft and their associated retainer rings that are employed in the prior art apparatus and method described above are eliminated. Only a single annular groove is formed in the shaft of the motor, the groove being the bottommost of the three grooves formed in the vertically oriented motor shaft of the prior art shown in FIG. 1. A retainer ring is inserted into the bottommost groove and the ring engages directly with the bottom of the bearing mounted on the motor housing end shield. What is meant by xe2x80x9cengages directlyxe2x80x9d is that the retainer ring is in direct contact with the bearing and there are no other intervening component parts positioned between the retainer ring and the bearing.
The spacer sleeve of the invention is then positioned over the top end of the shaft. A bottom, proximal end of the sleeve engages directly against the opposite side of the bearing from the retainer ring. This positions the opposite upper, distal end of the spacer sleeve vertically above the sleeve proximal end. The direct engagement of the sleeve proximal end on one side of the bearing and the direct engagement of the retainer ring on the opposite side of the bearing positively locates the sleeve distal end relative to the motor housing end shield and the shaft. What is meant by xe2x80x9cpositively locatesxe2x80x9d is that the position of the sleeve distal end relative to the motor housing and the shaft is a predetermined distance or length from the bearing mounted in the end shield. The position of the bearing mounted in the end shield of the motor housing is a predetermined or set position determined by the dimensions of the bearing and the recess provided in the end shield for the bearing, as well as the dimensions of the end shield itself. With the length of the sleeve between its opposite proximal and distal ends being a set or predetermined length, engaging the sleeve proximal end directly against the bearing positions the opposite distal end of the sleeve the predetermined distance from the bearing and thereby positively locates the sleeve distal end at a predetermined distance from the motor housing end shield. Thus, the spacer sleeve distal end provides a reference point for positively locating a machined surface on the end shield which can be used to engage with a housing of a pump driven by the motor to positively locate the pump housing relative to the motor and the motor shaft. The spacer sleeve distal end also provides a reference point for positively locating the rotating component, or impeller, of the pump.
The impeller is assembled onto the end of the shaft with the impeller (or a washer associated with the impeller) engaging directly with the sleeve distal end, thereby positively locating the impeller or other rotating component relative to the shaft and relative to a pump housing assembled to the motor. Because the tubular sleeve engages around the motor shaft, and the proximal end of the sleeve engages directly with the bearing supported in the motor end shield, assembling the pump to the motor and, in particular, the pump impeller to the end of the motor shaft, will not displace the sleeve relative to the shaft or the motor housing.
Thus, the spacer sleeve of the invention eliminates the problem of a retainer ring coming out of its shaft groove as the pump impeller is assembled onto the shaft. It also eliminates the possibility of the impeller becoming improperly positioned in the pump housing, and eliminates the possibility of the machined surface on the motor housing being incorrectly positioned which could result in the pump housing being improperly positioned relative to the motor shaft. The spacer sleeve also functions to retain the end shield bearing in place on the motor shaft and eliminates two annular grooves and their associated retainer rings previously needed on the shaft, resulting in a cost reduction in manufacturing the motor.